A carriage control tape was a loop of

punched tape Five- and eight-hole punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data storage ...

that was used to synchronize rapid vertical page movement in most IBM and many other

line printer A line printer prints one entire line of text before advancing to another line. Most early line printers were impact printers. Line printers are mostly associated with unit record equipment and the early days of digital computing, but the ...

s from unit record days through the 1980's. The tape loop was as long as the length of a single page. A pin wheel moved the tape accurately using holes in the center of the tape. A hole punched in one of the other channels represented a particular position on the page. Channel one was typically used to indicate the top of the page and might be the only channel used. Another channel might indicate the summary line on an invoice, enabling rapid skipping to that line. IBM provides a special manual punch that allowed accurate placement of the channel punches. Skipping occurred under computer control, but a form feed switch on the printer control panel allowed a manual skip to the top of the page. The tapes could be easily changed when new, continuously fed forms were loaded into the printer.

Forms control buffer

Newer printers use a "forms control buffer" (FCB), which is an electronic image of the physical carriage control tape. A job can request a specific FCB for a printout, and it will be loaded before printing is started, eliminating operator intervention.

Conventions

Conventionally, channel 1 indicates the top of the form (the first printable line on a page, often but not necessarily the first line of the page), and a new form is started with a "skip to channel 1" command (skipping is much faster than line spacing). Channel 9 is positioned a few lines above the end of the page, so a system that could sense the printer status while printing would, for example, have room to print a page footer or totals. Channel 12 indicates the last printable line of the form. These are only conventions, however, and applications are free to establish their own standards. File:IBM 1403 Printer opened.jpg, IBM 1403 printer opened up as it would be to change paper. Note carriage control tape in upper right. File:IBM 1403 side view open.agr.jpg.jpg, Side view of opened up IBM 1403 printer. File:IBM1403controltape.jpg, Close up of carriage control tape.

Sources

IBM 407 manual p.129 ff

Rack for holding carriage tapes
at

Computer History Museum The Computer History Museum (CHM) is a museum of computer history, located in Mountain View, California. The museum presents stories and artifacts of Silicon Valley and the information age, and explores the computing revolution and its impact on ...

* {{US patent, 3094261

External links

* Two IBM carriage control tape punches in the Computer History Museum collection

* Another image of a carriage control tape punch at ibmcolletables.com

IBM printers Computer storage tape media